Spatial light modulators together with adapted projection systems of so-called “maskless” lithographic systems replace reticles of conventional lithographic systems to provide for imaging onto photosensitive substrates patterns that are not limited by the physical boundaries or particular patterns of the reticles. Instead of imaging static patterns within the reticles, the maskless lithographic systems image dynamic patterns of focused spots that are individually switched between on and off states while being translated across the photosensitive substrates.
The spatial light modulators include an array of elements that are individually addressable for functioning as light switches that control a spatial distribution of light. The associated projection system focuses light regulated by each of the elements into a pattern of focused spots, which is relayed (or imaged directly) onto the photosensitive substrates. Typically, the projection system forms a magnified image of each of the individually addressable elements on corresponding microlenses of a microlens array, and the individual microlenses of the microlens array concentrate the light from the individual addressable elements through the focused spots.
Although both the focusing and magnification functions result in the focused spots being spaced apart, the pattern of focused spots includes multiple rows of focused spots and is oriented at a slight angle to a direction of translation with respect to the substrate so that successive rows of the focused spots provide for selectively illuminating any desired point on the substrate. The resolution at which a pattern can be printed onto the substrate relates to the size and shape of the focused spots as well as the radial distribution of light within the focused spots.